Grady Sizemore's determined comeback continues, and there's not a better story in baseball.

That's in March. Imagine if it's Memorial Day and Sizemore's still on the field, not the disabled list. Or if it's in September and he's trying to help the Red Sox qualify to defend their World Series championship in October?

Pretty cool.

The former All-Star, who has had seven surgeries since 2009, including microfracture procedures on both knees, remains in "a sincere competition" with Jackie Bradley Jr. for the Red Sox's center-field job, to use manager John Farrell's words.

But more and more, it looks like the 31-year-old Sizemore will be the guy playing center on Opening Day at Camden Yards. He went the distance for the first time in a 3-2 loss to the Yankees on Thursday night at JetBlue Park.

Sizemore did not reprise his spectacular work from Monday's World Series rematch against the Cardinals, but he was solid. Sizemore was 1-for-4, scored a run and looked like a working part in a $155 million machine.

And, most important, Sizemore stayed healthy.

"He came out of tonight fine," Farrell said.

We'll take the manager's word for it, because Boston's clubhouse was closed to reporters before Sizemore emerged from the trainer's room. That's understandable, given his long checklist of high-maintenance joints.

Up next for Sizemore, who is batting .360 with just one strikeout in 25 at-bats, is a stretch of games on three consecutive days, beginning in a Minor League game on Sunday after two days of workouts. If Sizemore's no worse for wear at the end of Tuesday's game against the Rays, he will have passed the final milestone on his unlikely road to becoming the official replacement for Jacoby Ellsbury.

Where would Sizemore have been on a list of possibilities last December, when Ellsbury signed with the Yankees? 100th? 1,000th?

This is a comeback with staggering audacity. It might lack the drama of Tony Conigliaro's return from his horrific beaning, but if the Red Sox can get 141 games from Sizemore, it would be just as impressive as it was when Conigliaro managed that workload in 1969.

If you are listening to the default sound bite, you're hearing only that Sizemore has missed the past two seasons, and that sells his challenge short. Way short. This is a guy who has been severely limited by bad knees for five years and threw in a back surgery as a bonus. If you know that, you grasp why it seemed crazily optimistic for Boston to sign him.

It helps Sizemore that Farrell had been the Indians' director of player development when he climbed through the farm system after being acquired from the Expos. They've got a bond, and the Red Sox did a good job of selling Sizemore on their medical staff, pointing toward David Ortiz's remarkable recovery from an Achilles tendon injury that at one point looked like the end of his career.

Still, modern baseball is a game of short memories and cold-hearted analysis. What were the Red Sox thinking?

Sizemore had played only 210 games in the three seasons before missing all of 2012 and '13 -- or 34 more than Dustin Pedroia played last year, with the postseason thrown in on top of suiting up for 160 games in the regular season. So that's 42 games per year over the past five years for Sizemore, who had begun his career as the Indians' version of Pedroia -- an everyday guy who won two American League Gold Glove Awards and regularly generated an OPS ranging from .832 to .907 over a four-year span.

How good of a player was Sizemore for the Indians? A three-time All-Star by age 25, he amazed the White Sox so often that Ozzie Guillen called him "Superman."

In Sizemore's first four full seasons, he averaged 6.2 WAR. That's better than what Ellsbury delivered to the Red Sox last season, and his performance convinced the Yankees to sign him to a $153 million contract.

Sizemore took a major step toward the team plane to Boston in that game against the Cardinals on Monday, when he turned in a performance worthy of the most recent World Series. He had three hits, including a double off the Green Monster, and made two heart-thumping catches, one in which he bounced off the wall and a second when he sprawled on the warning track.

Farrell said on Wednesday that "the needle still points to the north" regarding Sizemore. The next week will show whether he is physically ready for the daily grind of Major League Baseball.

Sizemore's best moment Thursday came with one of those "professional at-bats" that has a Red Sox trademark since the "idiots" broke the curse.

Sizemore fell into an 0-2 hole against David Phelps with pinch-runner Carlos Rivero on first and one out in the sixth inning. But Sizemore laid off a cutter that ran just outside and then spit on a slider in the dirt. The 2-2 pitch was nasty, but he knocked a grounder into right field through the hole opened up because Mark Teixeira was keeping Rivero close to first. It was a soft single, but it would set up a two-run double for Pedroia.

"His at-bats have been fairly consistent throughout all of Spring Training, regardless of the outcome," Farrell said. "There's been hard contact where he hasn't had anything to show for it. He hasn't been fooled by too many offspeed pitches. It's a direct swing, there's not a lot of movement and that's what has allowed him -- in addition to being a great athlete -- to come in and show like he has [after two years of not playing]."

Sizemore might not have become such a focus if Bradley was hitting .419, as he did last season when he won a job as the Opening Day left fielder. But the former University of South Carolina star didn't come out hitting. Farrell says "the consistency of the at-bats has been there," but Bradley, who is ranked the club's No. 3 prospect, has only eight hits in 40 Grapefruit League at-bats.

Bradley's .200 average is too much in line with the numbers he produced as a rookie, when he hit .189 in 37 games, mostly in bookend stints in April and September. But Farrell isn't measuring Bradley by his numbers.

"Speaking for all of us in camp, we couldn't be more proud of the way he's handled this," Farrell said. "He's a smart guy. He knows exactly the situation he's in. He's asked about it daily. You know what? He's not afraid to be himself as a player. He's not trying to be Jacoby Ellsbury or anybody else. He's Jackie Bradley, and he's doing the best he can. He's going about it absolutely the right way."

There was a thought that Sizemore was signed to push Bradley. But anyone who felt this situation was as simple as that didn't understand how hard Sizemore was willing to push himself. He's been doing it for years, as much as anyone in baseball, and it looks like that work is about to pay off.

Phil Rogers is a columnist for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.